Everyone needs their space. Sometimes that sacred space is violated and you need people to get the heck out of your room so you can recharge. However you don't want to be rude and being direct isn't in your nature; so you have to do it the passive aggressive way.
The best way to start is to "forget" how to have a conversation. don't say things that will help the conversation continue, use as little words as possible when responding. If you can manage keeping responses to one word that is good, if you can manage single word AND single syllable then you've got this down. Awkward silences in a conversation can be awful and you may want to break the silence. But it's important that you embrace these lulls. Relish in the silence, imagine the creeping need to leave sneak into their spines as each second goes by. You have all the power until they open their dumb mouths again.
If the person in question isn't getting these hints then it's time to change tactics a little bit. Change the subject to being somewhere else, anywhere. "Where in the world would you go if you could be anywhere?" "wouldn't you love to be out of here?". Once the topic has shifted to being somewhere else return to the strategy of using one word responses. Continue this cycle if they try to change the subject. Something you need to be careful about when asking this question is they might respond with something like "there's no place I'd rather be then here" in which case you have played yourself.
If things get too out of hand you can always just raise the stakes and make things get even more out of hand but in your favor. For example, set off the fire alarm, this is a very easy quick and affordable way to get your friend- and in fact the entire buildings occupancy to leave. The only draw back is you also have to leave as well so choose this option wisely and at your discretion.
Keep in mind that you still have to be friends with this person and what ever you end up doing will have an effect on the relationship so don't kill them or anything.
